Motor Vehicle

ABSTRACT

A motor vehicle has a motor performing power driving and regeneration. The motor has an inverter, a first power storage device with a large-capacity characteristic, a second power storage device with a high-power characteristic, a power converter and a circuit. The power converter has a voltage step down function during the power driving and a voltage step up function during the regeneration. In the circuit, the power converter, with the voltage step down function during the power driving, is connected to the first power storage device and the second power storage device is connected in series between a reactor of the power converter and the inverter. During the power driving of the motor, an output voltage of the first power storage device is stepped down to supply energy from the first power storage device and the second power storage device to the inverter.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Application No.2020-194410, filed Nov. 24, 2020. The disclosure of the aboveapplication is incorporating herein by reference.

FIELD

The present disclosure relates to a motor vehicle with a motorperforming power driving and regeneration and, more particularly, to apower storage device that supplies energy to the motor in driving modeand restore energy from motor in regeneration mode.

BACKGROUND

A motor vehicle described in Japanese Unexamined Patent ApplicationPublication No. 2018-166367 is an example of a motor vehicle with amotor configured to perform power driving and regeneration. A powerstorage device supplies energy to the motor. The motor vehicle canobtain a thrust by a drive force of the motor, and recover the energyinto the power storage device by adjusting a braking torque of a drivingwheel. According to this motor vehicle, the energy recovered duringbraking can be stored in the power storage device (battery) and used asdrive energy during the power driving.

In the related art described above, a voltage of the power storagedevice is set to a lower limit value of a DC voltage of an inverter or avalue lower than the lower limit value. Further, adjustment is made inaccordance with setting of the DC voltage of the inverter by stepping upan output voltage of the power storage device. Therefore, in a case ofusing a power storage device whose output voltage is higher than thelower limit value of the DC voltage of the inverter, the output voltageof the power storage device cannot be stepped down. This causes a rangewhere an actual inverter DC voltage cannot be adjusted to the set valueof the DC voltage of the inverter. Thus, in a case where the lower limitvalue of the DC voltage of the inverter is changed to a voltage lowerthan the voltage of the power storage device due to a change in motorspecifications or the like. Thus, a storage battery designed exclusivelyfor voltage needs to be used. Accordingly, this causes a problem in thata standard-voltage power storage device cannot be used.

Adjustment may be made in accordance with the set value of the DCvoltage of the inverter by stepping down the output voltage of the powerstorage device. In this case, however, the output voltage of the powerstorage device cannot be stepped up. This causes a range where theactual inverter DC voltage cannot be adjusted to the set value of the DCvoltage of the inverter. Similarly to the related art described above,the storage battery designed exclusively for voltage needs to be used.Accordingly, this causes a problem in that the standard-voltage storagebattery cannot be used.

SUMMARY

According to a first aspect of the disclosure, a motor vehicle includesa motor to perform power driving and regeneration. An inverter convertsa direct current into an alternating current. A first power storagedevice has a large-capacity characteristic. A second power storagedevice has a high-power characteristic. A power converter has a voltagestep down function during the power driving and a voltage step upfunction during the regeneration. The power converter, with the voltagestep down function during the power driving, is in a circuit connectedto the first power storage device and the second power storage deviceconnected in series between a reactor of the power converter and theinverter. During the power driving of the motor, an output voltage ofthe first power storage device is stepped down to supply energy from thefirst power storage device and the second power storage device to theinverter.

According to a second aspect of the disclosure, during the regenerationin the motor, the resultant output voltage combination of the inverterand the second power storage device may be stepped up to recover theenergy into the first power storage device and the second power storagedevice.

According to a third aspect of the disclosure, the motor vehicle mayfurther include a first switch forming a circuit connecting the powerconverter and the inverter without intervention of the second powerstorage device. A second switch forms a circuit connecting the powerconverter and the inverter via the second power storage device.Determination may be made about a power storage status of the secondpower storage device based on a voltage of the second power storagedevice. When the power storage status of the second power storage deviceis equal to or lower than a predetermined lower limit value during thepower driving of the motor, the first switch may be turned ON and thesecond switch may be turned OFF to supply the energy from the firstpower storage device to the inverter while stepping down the outputvoltage of the first power storage device.

According to a fourth aspect of the disclosure, the motor vehicle mayfurther include a first switch forming a circuit connecting the powerconverter and the inverter without intervention of the second powerstorage device. A second switch forms a circuit connecting the powerconverter and the inverter via the second power storage device.Determination may be made about a power storage status of the secondpower storage device based on a voltage of the second power storagedevice. When the power storage status of the second power storage deviceis equal to or higher than a predetermined upper limit value during theregeneration in the motor, the first switch may be turned ON and thesecond switch may be turned OFF to store regenerated energy in the firstpower storage device while stepping up a DC voltage of the inverter.

According to a fifth aspect of the disclosure, during current control ofthe inverter, a DC voltage of the inverter may be controlled based on arotation speed of the motor. When the rotation speed of the motor isequal to or lower than a predetermined rotation speed, the DC voltage ofthe inverter may be controlled to decrease as the rotation speed of themotor decreases.

According to a sixth aspect of the disclosure, when a rotation speed ofthe motor is equal to or lower than a predetermined rotation speedduring current control of the inverter, a DC voltage of the inverter maybe controlled based on a peak value of a motor line-to-line voltage.

According to a seventh aspect of the disclosure, the first power storagedevice may be a large-capacity lithium ion battery or a large-capacitynickel-metal hydride battery. The second power storage device may be ahigh-power lithium ion battery, a high-power nickel-metal hydridebattery, a lithium ion capacitor, or an electric double layer capacitor.

According to the present disclosure, the motor vehicle includes thepower converter with the voltage step down function during the powerdriving and the voltage step up function during the regeneration. Thepower converter, with the voltage step down function during the powerdriving, is in a circuit connected to the first power storage device andthe second power storage device connected in series between the reactorof the power converter and the inverter. During the power driving of themotor, the output voltage of the first power storage device is steppeddown to supply the energy from the first power storage device and thesecond power storage device to the inverter. In combination with theincrease in the voltage of the second power storage device, the inverterDC voltage can be stepped up and down relative to the output voltage ofthe first power storage device. Therefore, adjustment can be made inaccordance with a set voltage range of the inverter by stepping up anddown the output voltage of the first power storage device. Thus, even ifthe set value of the DC voltage of the inverter is changed, astandard-voltage storage battery can be used and an increase inmanufacturing costs can be prevented.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic diagram of a motor vehicle.

FIG. 2 is a circuit diagram of a power conversion device of the motorvehicle.

FIG. 3 is a conceptual diagram of the power conversion device of themotor vehicle.

FIG. 4 is a schematic diagram of control relationships in the motorvehicle.

FIG. 5 is a time chart of power control in the motor vehicle.

FIG. 6 is a flowchart of the overall power control in the motor vehicle.

FIG. 7 is a graph of request characteristics of the motor vehicle(vehicle requests on a driving wheel).

FIG. 8 is a graph of request characteristics of the motor vehicle (motorrequests on the driving wheel).

FIG. 9 is a graph of request characteristics of the motor vehicle(vehicle requests on a driven wheel).

FIG. 10 is a graph of request characteristics of the motor vehicle(brake requests on the driven wheel).

FIG. 11 is a flowchart of request process control in the power controlin the motor vehicle.

FIG. 12 is a graph of a driver's request table of the motor vehicle(Table 1).

FIG. 13 is a graph of a driver's request table of the motor vehicle(Table 2).

FIG. 14 is a graph of a driver's request table of the motor vehicle(Table 3).

FIG. 15 is a graph of a driver's request table of the motor vehicle(Table 4).

FIG. 16 is a graph of a driver's request table of the motor vehicle(Table 5).

FIG. 17 is a graph of a driver's request table of the motor vehicle(Table 6).

FIG. 18 is a flowchart of motor control in the power control in themotor vehicle.

FIG. 19 is a table of power conversion circuit control in the motorvehicle.

FIG. 20 is a graph of a voltage request table of the motor vehicle(Table A in a case of PWM).

FIG. 21 is a graph of a voltage request table of the motor vehicle(Table B in the case of PWM).

FIG. 22 is a graph of a voltage request table of the motor vehicle(Table C in the case of PWM).

FIG. 23 is a graph of a voltage request table of the motor vehicle(Table A in a case depending on a peak value of a motor line-to-linevoltage).

FIG. 24 is a graph of a voltage request table of the motor vehicle(Table B in the case depending on the peak value of the motorline-to-line voltage).

FIG. 25 is a graph of a voltage request table of the motor vehicle(Table C in the case depending on the peak value of the motorline-to-line voltage).

FIG. 26 is a time chart of an example of an operation depending on apeak value of a motor line-to-line voltage in a motor vehicle accordingto another embodiment.

FIG. 27 is a graph of a power storage status of a first power storagedevice of the motor vehicle.

FIG. 28 is a graph of a power storage status of a second power storagedevice of the motor vehicle.

FIG. 29 is a table of combinations of power storage devices of the motorvehicle.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described below in detail withreference to the drawings.

A motor vehicle according to each of the embodiments is a saddledvehicle, such as a motorcycle, traveling by using a drive force of amotor. As illustrated in FIGS. 1 to 4, the motor vehicle mainly includesa motor 1, an inverter 2, mechanical brakes (3 a, 3 b), a first powerstorage device 4, a second power storage device 5, an acceleratoroperator 6, a mechanical brake operator 7, a regenerative brake operator8, a power converter 10, an ECU 11, a start switch 12, and a monitor 13.

The motor 1 is an electromagnetic motor for obtaining a drive force byenergy supply. As illustrated in FIGS. 2 and 3, the motor 1 iselectrically connectable to the second power storage device 5, the powerconverter 10, and the first power storage device 4, via the inverter 2.The motor performs power driving and regeneration. The inverter 2 (DC-ACinverter) converts a direct current into an alternating current. In thisembodiment, the inverter 2 converts a direct current of the first powerstorage device 4 or the second power storage device 5 into analternating current, and supplies the alternating current to the motor1.

The mechanical brakes perform braking by releasing energy, as typifiedby a disc brake or a drum brake. The mechanical brakes are adriving-wheel mechanical brake 3 a that performs braking by releasingkinetic energy of a driving wheel Ta. A driven-wheel mechanical brake 3b performs braking by releasing kinetic energy of a driven wheel Tb. Thedriving-wheel mechanical brake 3 a and the driven-wheel mechanical brake3 b are connected to the mechanical brake operator 7 via a brakeactuator 9.

The mechanical brake operator 7 controls the mechanical brake(driven-wheel mechanical brake 3 b) to adjust a braking torque. In thisembodiment, an operation lever is attached to the right end of a handlebar. Based on an operation amount of the mechanical brake operator 7, amechanical brake controller 18 (see FIG. 4) may operate the brakeactuator 9 to actuate the driven-wheel mechanical brake 3 b.

The accelerator operator 6 controls the motor 1 to adjust a drive torqueof the driving wheel Ta. In this embodiment, an accelerator grip isattached to the right end of the handle bar. As illustrated in FIG. 4,based on an operation amount of the accelerator operator 6, an invertercontroller 16 may estimate a torque request and operate the motor 1 toobtain a desired drive force. The inverter controller 16 is onecontroller provided in the ECU 11.

The power storage devices supply energy to the motor 1. In thisembodiment, the power storage devices are the first power storage device4 and the second power storage device 5. The first power storage device4 is a storage battery with a large-capacity characteristic. Asillustrated in FIG. 29, examples of the first power storage device 4include a large-capacity lithium ion battery and a large-capacitynickel-metal hydride battery. The second power storage device 5 is astorage battery with a high-power characteristic. As illustrated in FIG.29, examples of the second power storage device 5 include a high-powerlithium ion battery, a high-power nickel-metal hydride battery, alithium ion capacitor, and an electric double layer capacitor.

The regenerative brake operator 8 controls the motor 1 to adjust abraking torque of the driving wheel Ta and recover the energy into thepower storage devices, first power storage device 4 and second powerstorage device 5. In this embodiment, an operation lever is attached tothe left end of the handle bar. Based on an operation amount of theregenerative brake operator 8, the motor 1 performs regeneration toobtain a desired braking force. Through the regeneration in the motor 1,the energy can be recovered into the first power storage device 4 andthe second power storage device 5.

The power converter 10 has a voltage step down function during the powerdriving of the motor 1 (during energy supply to the motor 1) and avoltage step up function during the regeneration in the motor 1 (duringenergy recovery from the motor 1). As illustrated in FIGS. 2 and 3, thepower converter 10 is connected between the first power storage device 4and the second power storage device 5 in an electric circuit. Morespecifically, as illustrated in FIG. 2, the power converter 10 includestwo semiconductor switching elements (MOSFETs) 10 a and 10 b and areactor 10 c (coil). The semiconductor switching elements 10 a and 10 binclude switches S1 and S2 and their body diodes, respectively.

In the power converter 10, according to this embodiment, the switches S1and S2 of the semiconductor switching elements 10 a and 10 b aresubjected to high-speed switching (duty control) to step down thevoltage during the power driving of the motor 1, when a current flowsrightward in FIG. 3, because the reactor 10 c is located on a downstreamside of the semiconductor switching elements 10 a and 10 b. The powerconverter steps up the voltage during the regeneration in the motor 1(when the current flows leftward in FIG. 3) because the reactor 10 c islocated on an upstream side of the semiconductor switching elements 10 aand 10 b.

More specifically, this embodiment provides, as illustrated in FIGS. 2and 3, a circuit where the power converter 10, with the voltage stepdown function during the power driving, is connected to the first powerstorage device 4. The second power storage device 5 is connected inseries between the reactor 10 c of the power converter 10 and theinverter 2. During the power driving of the motor 1, the power converter10 steps down an output voltage (Vdc) of the first power storage device4 to supply energy from the first power storage device 4 and the secondpower storage device 5 to the inverter 2. During the regeneration in themotor 1, the power converter 10 steps up the resultant output voltage(Vinv-Vc) of the combination between the inverter 2 and second powerstorage device 5 to recover the energy into the first power storagedevice 4 and the second power storage device 5.

As illustrated in FIG. 2, this embodiment provides a first switch S3forming a circuit connecting the power converter 10 and the inverter 2without intervention of the second power storage device 5. A secondswitch S4 forms a circuit connecting the power converter 10 and theinverter 2 via the second power storage device 5. The circuit of thisembodiment includes a switch Sa to be turned ON when the power converter10 is OFF, and stabilization capacitors Ca and Cb are connected to thecircuit. The first switch S3 and the second switch S4, according to thisembodiment, are formed in semiconductor switching elements (MOSFETs) 14and 15 (including their body diodes similarly to the semiconductorswitching elements 10 a and 10 b), respectively.

The ECU 11 controls the motor 1 in response to input driver requests. Asillustrated in FIG. 4, the ECU 11 includes the inverter controller 16, acircuit controller 17, and the mechanical brake controller 18, and isconnected to the inverter 2, the power converter 10, the first powerstorage device 4, the second power storage device 5, and the brakeactuator 9. The ECU 11 detects voltages of the first power storagedevice 4 and the second power storage device 5. It makes determinationon power storage statuses of the first power storage device 4 and thesecond power storage device 5 based on the voltages. FIG. 27 illustratesthe power storage status of the first power storage device 4. FIG. 28illustrates the power storage status of the second power storage device5.

When the power storage status of the second power storage device 5 isequal to or lower than a predetermined lower limit value (see FIG. 28),during the power driving of the motor 1, the first switch S3 is turnedON and the second switch S4 is turned OFF to supply energy from thefirst power storage device 4 to the inverter 2 while stepping down theoutput voltage (Vdc) of the first power storage device 4. When the powerstorage status of the second power storage device 5 is equal to orhigher than a predetermined upper limit value (see FIG. 28), during theregeneration in the motor 1, the first switch S3 is turned ON and thesecond switch S4 is turned OFF to store regenerated energy in the firstpower storage device 4 while stepping up a DC voltage (Vine) of theinverter 2.

The start switch 12 is an operation switch that enables the vehicle totravel. By operating the accelerator operator 6 after the start switch12 is operated, the motor 1 may be actuated for traveling. The monitor13 is an auxiliary device such as a liquid crystal monitor attached tothe vehicle. For example, the monitor 13 may display conditions of thevehicle (speed, power storage status, or whether malfunction hasoccurred) or a map of a navigation system.

As illustrated in FIG. 4, this embodiment provides a detector 19, asensor, detecting a rotation speed of the motor 1. When the rotationspeed of the motor 1, detected by the detector 19, is equal to or higherthan a predetermined value, a predetermined braking torque, based on anoperation amount of the regenerative brake operator 8, is generated byregenerative braking (particularly in this embodiment, generated only bythe regenerative braking). The maximum value of the predeterminedbraking torque during the regeneration in the motor 1 is a rated torqueof the motor 1.

When the rotation speed of the motor 1, detected by the detector 19, islower than the predetermined value, a braking torque is generated by themechanical brake (driving-wheel mechanical brake 3 a) based on theoperation amount of the regenerative brake operator 8. When the chargelevel of the first power storage device 4 is equal to or higher than apredetermined value, a braking torque is generated by the mechanicalbrake (driving-wheel mechanical brake 3 a) based on the operation amountof the regenerative brake operator 8.

According to the embodiment, FIG. 5 illustrates changes in parameters ina case where the accelerator operator 6 and the regenerative brakeoperator 8 are operated after the start switch 12 is turned ON in themotor vehicle. In particular, a capacitor current (Ic) and a capacitorcharge level (SOC2) are a current and a charge level of the second powerstorage device 5 of this embodiment. A battery current (Idc) and abattery charge level (SOC1) are a current and a charge level of thefirst power storage device 4 of this embodiment. In a table in FIG. 5,“function circuit control number” (FCCNO) corresponds to “FCCNO” inFIGS. 4, 18, and 19.

Next, control on the motor vehicle (main control), according to thisembodiment, is described with reference to a flowchart of FIG. 6.

In S1, determination is first made as to whether the start switch 12 isON. When determination is made that the start switch 12 is ON,determination is made in S2 as to whether a charge status (Soc1) of thefirst power storage device 4 is higher than a predetermined lower limitvalue (see FIG. 27). When determination is made that the charge status(Soc1) is higher than the predetermined lower limit value, a requestprocess (S3), motor control (S4), and mechanical brake control (S5) areperformed sequentially.

Next, according to this embodiment, request characteristics of the motorvehicle are described with reference to FIGS. 7 to 10.

The characteristics illustrated in FIG. 7 show the relationship betweena vehicle speed and both of the drive torque and the braking torque ofthe driving wheel Ta. The characteristics illustrated in FIG. 8 show therelationship between a motor torque of the driving wheel Ta and arotation speed (ω) of the motor 1. Particularly in a case of high-speedtraveling, FIG. 7 illustrates relationships where the drive torquegradually decreases and the braking torque is constant relative to thevehicle speed. In FIG. 8, a positive side, (upper half) from thevertical axis, shows a drive torque based on an operation amount of theaccelerator operator 6. A negative side, (lower half) from the verticalaxis, shows a braking torque based on an operation amount of theregenerative brake operator 8. In FIG. 8, reference symbol Tm1represents the rated torque of the motor 1.

The characteristics illustrated in FIG. 9 show the relationship betweenthe vehicle speed and a braking torque of the driven wheel Tb. Thecharacteristics illustrated in FIG. 10 show the relationship between abraking torque of the driven wheel Tb (mechanical braking torque (Tbmf))and the rotation speed (ω) of the motor 1. Since FIGS. 9 and 10illustrate the characteristics of the driven wheel Tb, only a negativeside, (lower half) from the vertical axis, shows the characteristics(braking torques).

Next, according to this embodiment, control on the motor vehicle(request process control) is described with reference to a flowchart ofFIG. 11.

In S1, determination is first made as to whether the regenerative systemis normal based on whether a malfunction signal is generated. Whendetermination is made that the malfunction signal is not generated,determination is made in S2 as to whether the accelerator operator 6 isoperated (whether an accelerator operation amount Ap is larger than 0).When determination is made that the accelerator operator 6 is operatedlarger than 0, the process proceeds to S5 for motor driving mode. Amotor torque (Tm), based on the operation amount of the acceleratoroperator 6, is calculated with reference to Table 1 illustrated in FIG.12.

After the calculation in S5, the process proceeds to S9 (driving wheelmechanical break). A mechanical braking torque (Tbmr), based on anoperation amount of the regenerative brake operator 8, is calculatedwith reference to Table 5 illustrated in FIG. 16. Then, the processproceeds to S13 (driven wheel mechanical break). A mechanical brakingtorque (Tbmf), based on an operation amount of the mechanical brakeoperator 7, is calculated with reference to Table 6 illustrated in FIG.17. The mechanical braking torque (Tbmr) calculated in S9 is the brakingtorque of the driving wheel Ta. The mechanical braking torque (Tbmf)calculated in S13 is the braking torque of the driven wheel Tb.

When determination is made in S2 that the accelerator operator is notoperated, determination is made in S3 as to whether the regeneration inthe motor 1 is possible. In S3, determination is made that theregeneration in the motor 1 is possible when the power storage status(Soc1) of the first power storage device 4 is equal to or lower than apredetermined upper limit value (see FIG. 27) and the rotation speed ofthe motor is equal to or higher than ω1 (see FIG. 8). When determinationis made that the regeneration in the motor 1 is possible, determinationis made in S4 as to whether the power storage status (Soc2) of thesecond power storage device 5 is higher than the predetermined upperlimit value (see FIG. 28).

When determination is made in S4 that the power storage status (Soc2) ofthe second power storage device 5 is higher than the predetermined upperlimit value (see FIG. 28), the process proceeds to S6 (powerregeneration to only first storage device. A motor torque (Tm), based onthe operation amount of the regenerative brake operator 8, is calculatedwith reference to Table 2 illustrated in FIG. 13. In the calculation ofthe motor torque (Tm), with reference to Table 2, when the rotationspeed of the motor 1 is equal to or lower than a predetermined rotationspeed (ω2) illustrated in FIG. 8, a correction is made such thatTm=Tm(ω−ω1)/(ω2−ω1). After the calculation in S6, the process proceedsto S10. A mechanical braking torque of driving wheel (Tbmr), based onthe operation amount of the regenerative brake operator 8, is calculatedwith reference to Table 4 illustrated in FIG. 15. Then, S13 issequentially performed as described above.

When determination is made in S4 that the power storage status (Soc2) ofthe second power storage device 5 is not higher than the predeterminedupper limit value (see FIG. 28), the process proceeds to S7. A motortorque (Tm), based on the operation amount of the regenerative brakeoperator 8, is calculated with reference to Table 3 illustrated in FIG.14. In the calculation of the motor ,torque (Tm) with reference to Table3, when the rotation speed of the motor 1 is equal to or lower than thepredetermined rotation speed (ω2) illustrated in FIG. 8, a correction ismade such that Tm=Tm(ω−ω1)/(ω2−ω1) similarly to Table 2. After thecalculation in S7, the mechanical braking torque (Tbmr) is set to 0 inS11, and then S13 is performed as described above.

When determination is made in S1 that the malfunction signal isgenerated or when determination is made in S3 that the regeneration isnot possible, the process proceeds to S8, and the motor torque (Tm) isset to 0. Then, the process proceeds to S12, and a mechanical brakingtorque (Tbmr), based on the operation amount of the regenerative brakeoperator 8, is calculated with reference to Table 5 illustrated in FIG.16. Thus, when determination is made that the regenerative system hasmalfunction or the regeneration is not possible, the braking torque canbe generated by the mechanical brake (driving-wheel mechanical brake 3a) based on the operation amount of the regenerative brake operator 8.This occurs after the calculation in S12, S13 is performed as describedabove.

Next, according to this embodiment, control on the motor vehicle (motorcontrol) is described with reference to a flowchart of FIG. 18.

In S1, determination is first made as to whether the regenerative systemis normal based on whether the malfunction signal is generated. Whendetermination is made that the malfunction signal is not generated,determination is made in S2 as to whether the accelerator operator 6 isoperated (whether the accelerator operation amount Ap is larger than 0).When determination is made that the accelerator operator 6 is operated,determination is made in S3 as to whether the power storage status(Soc2) of the second power storage device 5 is higher than thepredetermined lower limit value (see FIG. 28).

When determination is made in S3 that the power storage status (Soc2) ofthe second power storage device 5 is not higher than the predeterminedlower limit value (see FIG. 28), determination is made in S6 as towhether the rotation speed (ω) of the motor 1 is lower than ω3 (seeFIGS. 20 and 23). When determination is made that the rotation speed(ω)) of the motor 1 is not lower than ω3 (high-speed rotation), theprocess proceeds to S7, and function circuit control (FCC) is set to 1.When determination is made in S6 that the rotation speed (ω) of themotor 1 is lower than ω3 (low-speed rotation), the process proceeds toS8, and FCC is set to 2.

When determination is made in S3 that the power storage status (Soc2) ofthe second power storage device 5 is higher than the predetermined lowerlimit value (see FIG. 28), the process proceeds to S9, and FCC is set to3. When determination is made in S2 that the accelerator operator 6 isnot operated, determination is made in S4 as to whether the regenerationin the motor 1 is possible. In S4, determination is made that theregeneration in the motor 1 is possible when the power storage status(Soc1) of the first power storage device 4 is equal to or lower than thepredetermined upper limit value (see FIG. 27) and the rotation speed ofthe motor is equal to or higher than ω1 (see FIG. 8).

When determination is made in S4 that the regeneration in the motor 1 ispossible, determination is made in S5 as to whether the power storagestatus (Soc2) of the second power storage device 5 is higher than thepredetermined upper limit value (see FIG. 28). When determination ismade that the power storage status (Soc2) of the second power storagedevice 5 is higher than the predetermined upper limit value, the processproceeds to S10, and FCC is set to 4. When determination is made thatthe power storage status (Soc2) of the second power storage device 5 isnot higher than the predetermined upper limit value, the processproceeds to S11, and FCC is set to 5. When determination is made in S1that the malfunction signal is generated or when determination is madein S4 that the regeneration in the motor 1 is not possible, the processproceeds to S12, and FCC is set to 6.

After any one of the modes (FCC) from 1 to 6 is determined as describedabove, determination is made in S13 as to whether a mode determined in aprevious process (FCCO) is changed to the mode determined in the currentprocess (FCC). When determination is made that the mode is not changed,the process proceeds to S14, and the FCCNO determined in any one of S7to S12 is maintained. When determination is made that the mode ischanged, the process proceeds to S15, and (FCCNO) is set to 7. Then,control associated with the FCCNO is performed in S16. In S17, the modedetermined in the current process (FCC) is stored as FCCO. In S18,inverter control is performed.

The control in S16 is performed with reference to a control table ofFIG. 19. The following are details of the control in the control table.

When FCCNO=1, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are turned OFF (the power converter 10 is turnedOFF), the first switch S3 and the second switch S4 are turned OFF, andthe switch Sa is turned ON. In the control table, “capacitor seriesconnection” means a state where “the second power storage device 5 isconnected in series between the reactor 10 c of the power converter 10and the inverter 2”.

When FCCNO=2, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are subjected to duty control during the powerdriving. Thus, the power converter 10 steps down the output voltage ofthe first power storage device 4. Further, the first switch S3 is turnedON, the second switch S4 is turned OFF, and the switch Sa is turned OFF.When FCCNO=2, current control of the inverter 2 is performed withreference to Table A illustrated in FIG. 20.

According to Table A, when the current control of the inverter 2 isperformed under PWM control, the DC voltage of the inverter 2 iscontrollable based on the rotation speed (ω) of the motor 1, asillustrated in FIG. 20. When the rotation speed of the motor 1 is equalto or lower than the predetermined rotation speed (ω3), the DC voltageof the inverter 2 is controlled to decrease as the rotation speed of themotor 1 decreases. Also in Tables B and C described later, it is assumedthat the current control of the inverter 2 is performed under the PWMcontrol.

When FCCNO=3, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are subjected to duty control during the powerdriving. Thus, the power converter 10 steps down the output voltage ofthe first power storage device 4. Further, the first switch S3 is turnedOFF, the second switch S4 is turned ON, and the switch Sa is turned OFF.When FCCNO =3, the current control of the inverter 2 is performed withreference to Table A illustrated in FIG. 20 similarly to the case whereFCCNO=2.

When FCCNO=4, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are subjected to duty control during theregeneration. Thus, the power converter 10 steps up the inverter DCvoltage. Further, the first switch S3 is turned ON, the second switch S4is turned OFF, and the switch Sa is turned OFF. When FCCNO =4, thecurrent control of the inverter 2 is performed with reference to Table Billustrated in FIG. 21.

When FCCNO=5, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are subjected to duty control during theregeneration. Thus, the power converter 10 steps up the resultant outputvoltage of the inverter 2 and the second power storage device 5.Further, the first switch S3 is turned OFF, the second switch S4 isturned ON, and the switch Sa is turned OFF. When FCCNO =5, the currentcontrol of the inverter 2 is performed with reference to Table Cillustrated in FIG. 22.

When FCCNO=6, the switches S1 and S2 of the semiconductor switchingelements 10 a and 10 b are turned OFF (the power converter 10 is turnedOFF), and the first switch S3, the second switch S4, and the switch Saare turned OFF. When FCCNO=7, the switches S1 and S2 of thesemiconductor switching elements 10 a and 10 b are subjected to dutycontrol, and the first switch S3, the second switch S4, and the switchSa are turned OFF.

In the embodiment described above, Tables A to C are applied on thepremise that the current control of the inverter 2 is performed underthe pulse width modulation (PWM) control. Instead, the current controlof the inverter 2 may depend on a peak value of a motor line-to-linevoltage considering Pulse Amplitude Modulation (PAM) technique. That is,the PWM control is control for changing a width of a switching frequency(pulse width) (changing a current flow rate of the inverter) relative tothe predetermined inverter DC voltage. However, the control depending onthe peak value of the motor line-to-line voltage is controlled forchanging the DC voltage of the inverter depending on the peak value ofthe motor line-to-line voltage as illustrated in FIGS. 23 to 26.

In the case where the current control of the inverter 2 is performedunder the control depending on the peak value of the motor line-to-linevoltage, in Table A illustrated in FIG. 23, the DC voltage of theinverter 2 is controlled based on the peak value of the motorline-to-line voltage when the rotation speed of the motor 1 is equal toor lower than the predetermined rotation speed (ω3). In Table B, controlis performed as illustrated in FIG. 24. In Table C, control is performedas illustrated in FIG. 25. FIG. 26 is a time chart illustrating anexample of a switching operation of the inverter circuit and behavior ofthe motor line-to-line voltage and a fundamental wave of the motorline-to-line voltage in a case where the current is controlled withreference to any one of the tables in FIGS. 23 to 25. The inverter DCvoltage is equal to the peak value of the motor line-to-line voltage. Inthis time chart, the inverter DC voltage (Vine) agrees with a peak valueof the fundamental wave of the motor line-to-line voltage.

In the motor vehicle according to the embodiment described above, whenthe rotation speed of the motor 1 is equal to or higher than thepredetermined value, the predetermined braking torque, based on theoperation amount of the regenerative brake operator 8, is generated bythe regenerative braking. Thus, a braking torque intended by the drivercan be generated by the regenerative braking over a wide rotation rangeof the motor 1.

That is, the predetermined braking torque is generated only by theregenerative braking based on the operation amount of the regenerativebrake operator 8. Therefore, the braking force intended by the drivercan stably be obtained without a sense of discomfort about brakeactuation characteristics (response and brake application level)compared with a case where the predetermined braking torque is generatedby combining the mechanical brake and the regenerative braking duringhigh-speed rotation of the motor. Since the speed range for the use ofthe regenerative braking is wide, the energy regeneration efficiencyincreases and the frequency of use of the mechanical brake(driving-wheel mechanical brake 3 a) decreases. Thus, a decrease in thedurability of the mechanical brake component can be suppressed.

The maximum value of the predetermined braking torque during theregeneration in the motor 1 is the rated torque of the motor 1.Therefore, a sufficient braking torque intended by the driver can beobtained. Thus, the regenerated energy can be increased at thepredetermined rotation speed or higher. Further, the power converter isprovided with the voltage step down function during the power drivingand the voltage step up function during the regeneration. The energy isrecovered via the power converter 10 during the regeneration. Therefore,the predetermined braking torque can be generated only by theregenerative braking in a range covering lower-speed rotation comparedwith a system where the voltage is not stepped up during theregeneration. Thus, the regenerated energy can be increased.

When the rotation speed of the motor 1 is lower than the predeterminedvalue, the braking torque is generated by the mechanical brake(driving-wheel mechanical brake 3 a) based on the operation amount ofthe regenerative brake operator 8. In an extremely low-speed rotationrange of the motor 1, it is difficult to perform the regenerativebraking until the vehicle is stopped even though step-up control isperformed. Therefore, when the vehicle speed is lower than apredetermined value, the braking torque can securely be generated by themechanical brake instead of the regenerative braking.

The power storage devices are the first power storage device 4, with alarge-capacity characteristic, and the second power storage device 5,with a high-power characteristic. The motor vehicle includes the circuitwhere the power converter, with voltage step down function during thepower driving, is connected to the first power storage device 4 and thesecond power storage device 5 is connected in series between the reactor10 c of the power converter 10 and the inverter 2. During theregeneration in the motor 1, the energy is recovered into the firstpower storage device 4 and the second power storage device 5 by usingthe circuit. Thus, the rated torque can be generated only by theregenerative braking in a range covering higher-speed rotation comparedwith a motor rotation speed where the rated torque can be generated onlyin the first power storage device 4 during the regeneration in the motor1.

When the charge level of the first power storage device 4 is equal to orhigher than the predetermined value, the braking torque is generated bythe mechanical brake (driving-wheel mechanical brake 3 a) based on theoperation amount of the regenerative brake operator 8. Determination ismade that no more charging can be made when the charge level of thefirst power storage device 4 is equal to or higher than thepredetermined value. Even though the regenerative braking is difficult,the braking torque can securely be generated by the mechanical brakeinstead of the regenerative braking. This embodiment is applied to thesaddled vehicle. Even though the two brake operators, the regenerativebrake operator 8 and the mechanical brake operator 7, are provided, anincrease in costs can be avoided because there is no need to add a newoperator separately.

During the power driving of the motor, the output voltage of the firstpower storage device 4 is stepped down to supply the energy from thefirst power storage device 4 and the second power storage device 5 tothe inverter 2. The series combination of the converter 10 outputvoltage and the voltage of the second storage device 5 enable step up ofthe voltage at the inverter 2 DC terminals. The adjustment can be madein accordance with the setting of the DC voltage of the inverter 2 bystepping up and down the resultant output voltage of the first powerstorage device 4 and the second power storage device 5. Therefore, evenif the set value of the DC voltage of the inverter 2 is changed, astandard-voltage storage battery can be used and an increase inmanufacturing costs can be prevented.

Particularly in this embodiment, the switches S1 and S2 of thesemiconductor switching elements 10 a and 10 b of the power converter 10are subjected to duty control during the power driving to optimally stepup and down the inverter DC voltage of the motor 1 relative to thevoltage of the first power storage device 4 combined with the secondpower storage device 5. Further, the supplied power driving energy isshared by the first power storage device 4 and the second power storagedevice 5. Therefore, the current of the first power storage device 4 issmaller than in a case where the same amount of power driving energy issupplied only by the first power storage device 4. Thus, even if thepower driving energy is large, the current of the first power storagedevice 4 can be kept small and the life of the first power storagedevice 4 can be prolonged.

The first switch S3 and the second switch S4 are provided anddetermination can be made about the power storage status of the secondpower storage device 5 based on the voltage of the second power storagedevice 5. When the power storage status of the second power storagedevice 5 is equal to or lower than the predetermined lower limit valueduring the power driving of the motor 1, the first switch S3 is turnedON and the second switch S4 is turned OFF to supply energy from only thefirst power storage device 4 to the inverter 2 while stepping down theoutput voltage of the first power storage device 4. Thus, even if thecharge in the second power storage device 5 is empty, the power drivingof the motor 1 can be continued by using the energy of the first powerstorage device 4, thereby allowing the vehicle to travel.

The first switch S3 and the second switch S4 are provided anddetermination can be made about the power storage status of the secondpower storage device 5 based on the voltage of the second power storagedevice 5. When the power storage status of the second power storagedevice 5 is equal to or higher than the predetermined upper limit valueduring the regeneration in the motor 1, the first switch S3 is turned ONand the second switch S4 is turned OFF to store regenerative energy inthe first power storage device 4 while stepping up the DC voltage of theinverter 2. Thus, even if the charge in the second power storage device5 is full, the regeneration in the motor 1 can be continued by storingthe regenerative energy in the first power storage device 4.

During the current control of the inverter 2, the DC voltage of theinverter 2 is controllable based on the rotation speed of the motor 1.When the rotation speed of the motor 1 is equal to or lower than thepredetermined rotation speed, the DC voltage of the inverter 2 iscontrolled to decrease as the rotation speed of the motor 1 decreases.Therefore, the DC voltage of the inverter 2 can be reduced duringlow-speed rotation, and instantaneous power of the switches can bereduced. Thus, the switching loss can be reduced during the low-speedrotation.

When the rotation speed of the motor 1 is equal to or lower than thepredetermined rotation speed during the current control of the inverter2, the DC voltage of the inverter 2 is controlled based on the peakvalue of the motor line-to-line voltage. Therefore, a fixed PAMswitching pattern for reducing the low-order harmonic component having aswitching frequency that is about three times as high as the fundamentalwaveform frequency can be used as the switching pattern. Thus, theswitching frequency can become 1/30 or lower than switching frequency inthe PWM control (duty control at a constant inverter DC voltage), andthe switching loss can become 1/30 or lower than switching loss in thePWM control.

Although the embodiments are described above, the present disclosure isnot limited to the embodiments. For example, the first power storagedevice 4 may be a power storage device in another form having alarger-capacity characteristic than the second power storage device 5.The second power storage device 5 may be a power storage device inanother form having a higher-power characteristic than the first powerstorage device 4. The semiconductor switching element may be an IGBT inplace of the MOSFET. The present disclosure may be applied to a vehiclewithout the monitor 13, or to a three-wheel or four-wheel vehicle suchas a buggy.

The present disclosure is also applicable to a motor vehicle with adifferent appearance or with other functions as long as thepredetermined braking torque based on the operation amount of theregenerative brake operator is generated by the regenerative brakingwhen the rotation speed of the motor is equal to or higher than thepredetermined value.

The present disclosure has been described with reference to thepreferred embodiment. Obviously, modifications and alternations willoccur to those of ordinary skill in the art upon reading andunderstanding the preceding detailed description. It is intended thatthe present disclosure be construed to include all such alternations andmodifications insofar as they come within the scope of the appendedclaims or their equivalents.

What is claimed is:
 1. A motor vehicle comprising: a motor performingpower driving and regeneration; an inverter converting a direct currentinto an alternating current; a first power storage device having alarge-capacity characteristic; a second power storage device having ahigh-power characteristic; a power converter having a voltage step downfunction during the power driving and a voltage step up function duringthe regeneration; and a circuit where the power converter, with thevoltage step down function during the power driving, is connected to thefirst power storage device and the second power storage device isconnected in series between a reactor of the power converter and theinverter, wherein, during the power driving of the motor, an outputvoltage of the first power storage device is stepped down to supplyenergy from the first power storage device and the second power storagedevice to the inverter.
 2. The motor vehicle according to claim 1,wherein, during the regeneration in the motor, an output voltage of thesecond power storage device combined with inverter voltage is stepped upto recover the energy into the first power storage device and the secondpower storage device.
 3. The motor vehicle according to claim 1, furthercomprising: a first switch forming a circuit connecting the powerconverter and the inverter without intervention of the second powerstorage device; and a second switch forming a circuit connecting thepower converter and the inverter via the second power storage device,wherein determination is made about a power storage status of the secondpower storage device based on a voltage of the second power storagedevice, and when the power storage status of the second power storagedevice is equal to or lower than a predetermined lower limit valueduring the power driving of the motor, the first switch S3 is turned ONand the second switch S4 is turned OFF to supply the energy from onlythe first power storage device to the inverter while stepping down theoutput voltage of the first power storage device.
 4. The motor vehicleaccording to claim 2, further comprising: a first switch forming acircuit connecting the power converter and the inverter withoutintervention of the second power storage device; and a second switchforming a circuit connecting the power converter and the inverter viathe second power storage device, wherein determination is made about apower storage status of the second power storage device based on avoltage of the second power storage device, and when the power storagestatus of the second power storage device is equal to or higher than apredetermined upper limit value during the regeneration in the motor,the first switch is turned ON and the second switch is turned OFF tostore regenerated energy in the first power storage device whilestepping up a DC voltage of the inverter.
 5. The motor vehicle accordingto claim 1, wherein, during current control of the inverter, a DCvoltage of the inverter is controllable based on a rotation speed of themotor, and when the rotation speed of the motor is equal to or lowerthan a predetermined rotation speed, the DC voltage of the inverter iscontrolled to decrease as the rotation speed of the motor decreases. 6.The motor vehicle according to claim 1, wherein, when a rotation speedof the motor is equal to or lower than a predetermined rotation speedduring current control of the inverter, a DC voltage of the inverter iscontrolled based on a peak value of a motor line-to-line voltage.
 7. Themotor vehicle according to claim 1, wherein the first power storagedevice is a large-capacity lithium ion battery or a large-capacitynickel-metal hydride battery, and the second power storage device is ahigh-power lithium ion battery, a high-power nickel-metal hydridebattery, a lithium ion capacitor, or an electric double layer capacitor.